The incorporation of flavorants in tobacco products is an important development in the tobacco industry due to the lowered aromaticity of the available tobacco and to the increased preference of some smokers for filter cigarettes. The addition of certain desirable flavorants to tobacco is limited by their volatility which causes them to be lost or diminished in quantity during processing and storage of the tobacco product. This problem is even more acute for filter cigarettes containing active adsorbent, such as charcoal, in the filters. During the processing and storage of this type of product, volatile flavorants migrate from the tobacco and are irreversibly bound by the active adsorbent, thereby depleting the flavorant in the product and possibly altering the effectiveness of the active adsorbent in its selective removal of undesirable smoke components.
A variety of flavorants have been developed and proposed for incorporation into tobacco products. Illustrative of such tobacco flavorants are those described in U.S. Pat. Nos. 3,580,259; 3,625,224; 3,722,516; 3,750,674; 3,879,425; 3,881,025; 3,884,247; 3,890,981; 3,903,900; 3,914,451; 3,915,175; 3,920,027; 3,924,644; 3,937,228; 3,943,943; 3,586,387; and the like. The tobacco flavorants include compounds such as succinic anhydride; dihydroxyacetone; substituted pyridines; cinnamic derivatives; isovaleric acid; 6-methylhepta-3,5-dien-2-one; 2-butyl-2-butenal; 1,3-cyclohexadiene; alpha-pyrones; substituted butyrolactones; pyrazines and thiazolidines; and the like.
U.S. Pat. No. 3,139,888 suggests the use of isoprenoid alcohols to impart desirable flavor to tobacco. U.S. Pat. No. 3,589,372 recommends the incorporation of a polyisoprenoid hydrocarbon into tobacco products as a flavor enhancer.
The high degree of volatility and ease of sublimation of flavorant additives in tobacco products have presented problems in the manufacturing operations and, in addition, have resulted in a decreased shelf-life of the products due to losses of flavorant by diffusion on storage.
In an attempt to alleviate these problems, it has been suggested that a tobacco flavorant might be adsorbed on a suitable support, such as activated charcoal or fuller's earth, and that the resultant composition might then be added to the tobacco. Attempts to pursue this method have not been satisfactory. The flavorant yields from such adsorbents have been found to be very low. Moreover, this method obviously necessitates incorporation of the adsorbent into the tobacco, and such a foreign material can result in an undesirable appearance as well as give rise to uneven burning of the tobacco.
In order to overcome these difficulties, a flavorant such as menthol has been incorporated into the tobacco as a part of a compound (i.e., a menthol-release agent) in such form that upon burning of the tobacco, the compound is decomposed to yield the desired menthol flavorant. While considerably more satisfactory than earlier attempts, even this technique has evidenced certain drawbacks.
Bavley et al., U.S. Pat. No. 3,312,226, describes a process whereby menthol is incorporated into tobacco as the carbonate ester of various alcohols, particularly one such as linalool, which are themselves useful flavorants. Upon pyrolysis of these carbonate esters, incident to the normal burning temperatures of the tobacco, the menthol is released to flavor the smoke. However, these simple carbonate esters have not proven wholly satisfactory. They retain one of the difficulties of menthol itself, in that they are somewhat susceptible to migration in the tobacco, and thereby prevent the strict control of quantitative release of menthol to the tobacco smoke during burning.
The Mold et al U.S. Pat. Nos. 3,332,428 and 3,419,543, offer a slightly different approach to the problem of adding menthol flavor to a tobacco smoke. These patents, like that of Bavley et al, rely upon the formation of a carbonate ester to bind the menthol in a release agent.
The Rundberg, Jr. et al. U.S. Pat. No. 3,887,603 describes the development of a new type of menthol-release agent for imparting menthol flavor to tobacco smoke with a high efficiency of menthol release upon pyrolysis under normal smoking conditions. The menthol-release agent is a polymeric l-menthyl carbonate ester composition characterized by the presence of a tertiary alcohol ester attachment.
U.S. Pat. Nos. 3,047,431 and 3,047,432 describe clathrate complexes which release flavorants to tobacco products under normal smoking conditions. Clathrate complexes have the disadvantage that they tend to dissociate when dissolved in solvents for the purpose of treating tobacco. Also, a clathrate complex additive tends to be unstable on tobacco due to the moisture in the tobacco, thereby releasing the complexed flavorant.
U.S. Pat. No. 3,047,433 describes Diels-Alder adducts which release flavorants to tobacco under normal smoking conditions. Such Diels-Alder adducts do not release flavorants efficiently, and they tend to produce undesirable side products under smoking conditions.
As it is apparent, the use of the diverse types of tobacco flavorants is characterized by various disadvantages. Some flavorants are prohibitively expensive. Other flavorants are complex mixtures of variable constituency and are inconsistent in effect. Other flavorants are too volatile for cigarette packaging and storage purposes. Still other prior art flavorants have a fragrance which impart undesirable aroma characteristics to tobacco products or which do not adequately improve the taste, character, and flavor of smoking tobacco. As a further disadvantage, conventional tobacco flavorants as described hereinabove either do not enhance the flavor and aroma of sidestream cigarette smoke or they may in fact impart an undesirable harshness to sidestream cigarette smoke.
Accordingly, it is a main object of this invention to provide smoking tobacco compositions having incorporated therein a flavorant which is characterized by lack of mobility and/or volatility at ambient temperature.
It is another object of this invention to provide smoking tobacco compositions having incorporated therein a polymeric composition which is adapted to release flavorant of enhancing character to tobacco smoke under normal smoking conditions, with high efficiency and without masking of the natural flavor of the resultant mainstream tobacco smoke.
It is another object of this invention to provide smoking tobacco compositions having incorporated therein a flavorant-release composition which under normal smoking conditions imparts improved flavor and aroma to sidestream cigarette smoke.
It is a further object of this invention to provide novel carbonate ester resin compositions which are adapted to be incorporated into tobacco compositions, and which under normal smoking conditions release an isoprene, anethole or menthene type of tobacco flavorant.
Other objects and advantages of the present invention shall become apparent from the following description and examples.